While that would be a wonderful addition, I doubt it will ever happen. Serviio is developed by a single person, and I doubt he has the resources to create such an app. That would require access to a wide variety of TVs to develop on, and there's really no way to pay for something like that. Even Plex has had to move away from charging for their apps, and the costs have to be recouped somehow. Plex does it with the Plex Pass, but that requires a significant investment by the company for their support servers, bandwidth, etc.

Since virtually every smart TV supports DLNA playback, building to that standard is the most cost effective for the small developer. Especially since the vast majority of online streaming devices (Blu Ray players, Roku, Nvidia Shield, etc.) also support DLNA in some fashion.